Gas gauge issue...

[Steve Shauger]

When it reads full the fuel sender is resistor is open therefore infinite resistance so it reads full. Check the resistance of the sender directly first and if ok check the wiring from the sender to the guage.

[169indy]

Originally Posted by Steve Shauger

When it reads full the fuel sender is resistor is open therefore infinite resistance so it reads full. Check the resistance of the sender directly first and if ok check the wiring from the sender to the guage.

The GM senders operative Zero to Ninety Ohms full scale range.
0 ohms Empty
90 ohms Full

An Open or infinite resistance will drive the gage to the right way past full indication.

Servicing sheet attached.

I built a "Gage sender" simulator that can be temporary installed in place of the Gas tank sender to the Car wiring and drive the Gage while sitting in the drivers seat. The Same can be accomplished by using a Resistance Decade box, but this tool is plug and play.
JIM

[67since67]

Testing can also be accomplished shade-tree style with a known good gauge sender and jumper leads to the sender harness and ground, to either condemn or rule out the sender. Or, just ground the sender connection and see if it goes to empty.